SVI-C Linkage for Allylsulfonximines via BF3-Mediated Allylation

Friedel-Crafts Reactivity with Sulfondiimidoyl Fluorides for the Synthesis of Heteroaryl Sulfondiimines

Sulfur functional groups are ubiquitous in molecules used in the pharmaceutical and agrochemical industries, and within these collections sulfones hold a prominent position. The double aza-analogues of sulfones, sulfondiimines, offer significant potential in discovery chemistry but to date their applications have been limited by the lack of convenient synthetic routes. The existing methods mainly rely on imination of low-valent-sulfur intermediates, or the combination of pre-formed organometallic reagents and electrophilic S(VI)-functionalities. Herein, we describe a Friedel-Crafts-type reaction of sulfondiimidoyl fluorides with (hetero)aryls. This new SuFEx reactivity benefits from broad functional group tolerance, mild reaction conditions, and does not require the use of pre-formed organometallic reagents. The efficient use of unprotected indoles and pyrroles, as well as furan, thiophene and carbocyclic aromatics, further demonstrates the advantages of these reactions. We show that the reactivity of the sulfondiimidoyl fluorides can be tuned by switching the N-substituents, allowing an expansion of the range of coupling partners. The utility of the transformation is exemplified by the synthesis of the sulfondiimine analogue of the HIV-I reverse transcriptase-inhibitor L-737,126.

Theoretical Insights into the Mechanism and Origin of Solvent-Dependent Selectivity in the Cyclization of Propargyl Alcohols for the Divergent Synthesis of N-Heterocycles

This study elucidates the mechanisms and principles governing chemoselectivity in synthesizing two distinct N-heterocycles, benzimidazole thiazine and benzothiazole imidazole, through BF3•OEt2-catalyzed cyclization reactions of propargyl alcohols with benzimidazole thiols. Employing density functional theory calculations, we highlight the crucial role of fluorine source in influencing chemoselectivity. In DCM, BF3, as the catalytic center, coordinates with propargyl alcohol's hydroxyl group to form a precursor. Conversely, in DMF, [BF2•DMF]+, formed from DMF and BF3•OEt2, acts as the catalytic center, activating the propargyl alcohol's hydroxyl group. The mechanisms in both solvents involve sequential steps: B-O bond formation, C-O bond cleavage, S-C bond formation, hydrogen atom transfer (HAT), cyclization, and deprotonation. A notable difference is the HAT process: in DCM, it follows a 1,5-HAT process, while in DMF, BF4- formation from DMF and BF3•OEt2 provides a fluorine source and introduces steric hindrance, favoring a 1,6-HAT process and leading to unique chemoselectivity. This pioneering research showcases the impact of DMF on cyclization reactions, offering valuable insights for comprehending and designing reactions driven by fluorine sources. Crucially, our results propose an innovative reaction mechanism featuring lower potential energy surfaces, enhancing our understanding of the intricate interplay among reactants, catalysts, and solvents.

C-SuFEx linkage of sulfonimidoyl fluorides and organotrifluoroborates

Sulfur(VI) fluoride exchange, a new type of linkage reaction, has excellent potential for application in functional molecule linkage to prepare pharmaceuticals, biomolecules, and polymers. Herein, a C-SuFEx reaction is established to achieve fast (in minutes) linkage between sulfonimidoyl fluorides and aryl/alkyl organotrifluoroborates. Potassium organotrifluoroborates are instantaneously activated via a substoichiometric amount of trimethylsilyl triflate to afford organodifluoroboranes, releasing BF3 as an activating reagent in situ. This sulfur(VI) fluoride exchange technique is capable of forming S(VI)-C(alkyl), S(VI)-C(alkenyl) and S(VI)-C(aryl) bonds, demonstrating its broad scope. Natural products and pharmaceuticals with sensitive functional groups, such as valdecoxib, celecoxib and diacetonefructose, are compatible with this protocol, allowing the formation of diverse sulfoximines.